JP Morgan CEO Jamie Dimon admitted his bank failed to monitor itself properly. This debacle is now an issue in the Massachusetts Senate race.

Democratic candidate Elizabeth Warren wants to paint incumbent Senator Scott Brown as part of an establishment that’s failed to put teeth in new banking regulation laws. The tactic plays to the strength of Warren’s resume, but puts her somewhat at odds with her own party leadership.

For Warren, campaigning Monday at Casey’s Diner in Natick was a welcome chance to showcase her record as a financial-industry critic and contrast it with Scott Brown.

“He was described as someone who really delivers for Wall Street,” says Warren. “I’ve been out there fighting the big financial institutions long before I ever got into a political race.”

But Warren’s pitch has a problem: Dimon is a Democrat who’s been publicly praised by President Obama. He was talked about as a possible Treasury Secretary in the administration.

“All I can say is for me, this has never been about party politics, it’s really been about who stands on the side of the people,” says Warren. “Jamie Dimon has led the charge to delay, to slow down, to put more loopholes into the implementation of Dodd-Frank.”

In a statement late Monday, Senator Brown called for a full investigation of the Chase fiasco, and if it reveals wrongdoing or risk to taxpayers, “Dimon should resign, because the buck stops with him.”